Plotting with plt.plot()

The plt.plot() function is the most commonly used method in Matplotlib. It lets you create simple line plots by specifying the data points for the x-axis and y-axis.

If you only pass one list of values, Matplotlib assumes it’s the y-axis and automatically assigns numbers starting from 0 for the x-axis.

When both x and y values are provided, Matplotlib connects the dots with a straight line by default.

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import matplotlib.pyplot as plt

x = [1, 2, 3, 4, 5]
y = [10, 20, 25, 30, 40]

plt.plot(x, y)
plt.title("Sample Line Plot")
plt.xlabel("X-axis")
plt.ylabel("Y-axis")
plt.show()

• The order of x and y matters — both lists must be the same length.
• If the plot looks wrong, check that your data is properly aligned.

You can also plot a list of values without specifying x. In that case, the x-axis will automatically be set to [0, 1, 2, ...].

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y = [5, 9, 4, 7]

plt.plot(y)
plt.title("Auto X-Axis")
plt.ylabel("Y Values")
plt.show()

This is useful for quick visual checks of any 1D data.

Now that you’ve learned how to plot lines using plt.plot(), the next step is to learn how to customize the lines with different colors, markers, and styles.